Caption: Lamp radiation, thermogram footage. Thermography records the temperature of surfaces by detecting long-wavelength infrared radiation. The colours show variations in temperature. The scale runs from white (warmest), through yellow, orange, red and purple to blue (coldest). This footage shows a person's hand held up to a lamp's light bulb (right) which is heating up after being turned on. The bulb heats up and radiates heat directly onto the hand (white area) until it is too hot for the person to hold their hand near it.